This invention relates generally to gas turbine engines, and more specifically to methods and apparatus for assembling gas turbine engines.
At least some known gas turbine engines used with aircraft include a core engine having, in serial flow arrangement, a compressor which compresses airflow entering the engine, a combustor which burns a mixture of fuel and air, and low and high pressure rotary assemblies which each include a plurality of rotor blades that extract rotational energy from airflow exiting the combustor to generate thrust from the engine. In addition, within at least some known gas turbines some of the work generated by the rotary assemblies is transmitted to an engine accessory gearbox by means of shaft wherein the available work can then be used to drive electrical equipment utilized on the aircraft.
As aircraft accessory power demands have increased, there also has been an increased need to run the gas turbine engines at idle speeds that may be higher than other engines not subjected to increased power demands. More specifically, increasing the idle speeds enables the increased power demands to be met without sacrificing compressor stall margins. However, the increased idle speeds may also generate thrust levels for the engine which are higher than desired for both flight idle decent operations and/or during ground idle operations. Over time, continued operation with increased thrust levels during such idle operations may increase maintenance costs and the increased fuel flows may also increase aircraft operating expenses.